This invention relates to a repairing method with welding, a welding method and a welding apparatus for a metal member. This invention can be applied to restore the shape or size of many kinds of metal equipment (hereinafter referred to as a metal member), such as metal molds for plastic jet molding or blow molding, metal molds for molding, metal molds for die casting, metal molds for glass molding or metal molds for press forming. In addition, this invention can be applied to repair or modify a relatively minute collapsing or flawed portion of, such a metal member.
In a general process to manufacture a new metal mold in a metal mold factory, the following problems commonly occur:
a) The metal member is over-scraped in a cutting process by a numerical control machine tool, such as a milling machine, with an input mistake, over-scraped by a manual machine tool through careless mistake, or over-scraped in a manual process with a file. PA1 b) The metal member is damaged or bit by a secondary discharge (arc discharge) of an electric discharge machine. PA1 c) A beaten mark, recession or flaw appear on the metal member from a hammer or a tool being dropped on the metal member or by hitting the metal member with a tool. These are caused by careless mistakes during a complex procedure or a lack of skill. PA1 d) It is necessary to modify a thickness of a resin in a product evaluation by a test molding or by making the resin thicker in order to prevent flash from appearing. PA1 e) An inner corner is curved in order to modify or change a design, or a height of the metal member is increased in order to change the scale thereof. PA1 f) The resin forms a parting line in the metal mold. Thus, the parting line may become hollow after the forming process is done several tens or hundreds of times. PA1 g) A cavity, core, gnawn portion or the like may be gnawn or worn out during the forming process. The flaw may be made when a tool is carelessly used. PA1 (1) It is necessary to repair the abrasion, obtuseness or collapse of the parting line of the metal mold. PA1 (2) It is necessary to repair the abrasion, obtuseness or collapse of a corner of an edge portion and a triangular portion. PA1 (3) A gnawn flaw of a sliding portion needs repair. PA1 (4) A pin hole needs repair. PA1 (5) It is necessary to repair an under-cut, flaw, blow hole or pit after an argon arc spot welding. PA1 (6) A corner should be modified when it is redesigned to be curved. PA1 (7) It is necessary to repair the gnawn flaw, an edge loss of a core pin or an ejector pin and to increase its height partially. PA1 (8) It is necessary to repair the gnawn part of the metal molds for the rubber molding or the blow molding or a flaw in a driving pin. PA1 (9) It is needed to repair a gnawn, a pushed cut or a butt portion. PA1 (10) It is necessary to repair the loss of a raised core having a minute thickness. PA1 (11) It is needed to repair a metal mold whose edge is a sharp knife shape.
The following problems occur in a molding or casting factory using metal molds for plastic molding or rubber molding, metal molds for die casting or press metal molds:
In other words, it is necessary frequently to repair, correct or modify the metal member in the factory as follows:
The metal molds for the plastic molding or rubber molding, the metal molds for the die casting or the press metal molds are very useful in many kinds of industrial fields for mass production, high quality and uniformity of industrial products. Expensive machine tools and operators are needed to make the metal molds. Moreover, the metal mold should be manually ground by skilled workers. Thus, the metal mold is expensive and requires many days to make. For example, a cheap metal mold may be one million yen and a large metal mold or a precise metal mold may be fifty million yen. In the case of a manufacturing line of automobiles that needs products formed by the metal molds, the motorcars should be manufactured in accordance with a schedule and penalties may be imposed when the manufacturing line stops. If the metal mold cannot be used because of small flaw or crash, the manufacturing plan may be affected and an economical loss may occur. It becomes absolutely necessary to repair the metal mold.
In the prior art, the argon arc spot welding is generally used to repair the over-scraped in the manufacturing process of the metal mold, to change the design or to modify it. However, repair by argon arc spot welding has the following problems. First, since the arc temperature of the argon arc spot welding is high, such as 6000-8000 degrees C., the welded metal may shrink. Thus, a shrinkage problem may occur, i.e., a boundary between the heat affected portion and the welded metal or the bonded peripheral area becomes hollow. There are many kinds of "shrinkage" sizes. In general, the "shrinkage" is 1-4 mm in width and 1/100-5/100 mm in depth. Since the metal mold in the molten pool produces gas by itself and the argon gas and air are captured in the molten pool, a blow hole and pit may occur in the welded metal. In addition, the metal mold may be changed in shape and color by adding a heat to the metal mold. An under-cut frequently occurs.
Second, an argon torch takes up much space, so that it may be impossible to weld a small area and build-up welding may be very difficult at the inner corner. When the edge or flaw of the core pin is welded, the heat effect may bend the whole core pin and the peripheral area having no relation to the build-up welding may be bent or changed in color. Even if the color-changed product is ground, a pattern based on the metal organization change is added to the plastic product. The formed product looks bad and product value is reduced. The argon arc spot welding has many disadvantages, i.e., this welding is difficult if a worker is not skilled; a metal mold part, such as the core pin, and a fine ridge-line (rib), such as the parting line, melt by the high temperature; the heat effected portion and the relieving portion are brittle because of the high temperature; and the finishing is difficult because an excessive portion of the welding is large.
Repair by a silver brazing is relatively simple and has good bonding characteristics. However, the silver brazing cannot be used to deposit the metal mold material. The silver brazing material is soft, so that a flaw may occur by hitting. Moreover, it is not durable. When the whole metal mold should be heated by gas, the metal mold may change in shape and color. The total braze may melt when executing a second brazing.
A build-up plating is proper for repairing a large area. However, this build-up plating requires a long time and is often not realistic. The metal mold material cannot be plated. In addition, the deposition is weak, and it is easy to separate the plate. The plate liquid corrodes the metal mold and is dangerous for workers.
A beater mechanism is a conventional manner for repairing the parting line by beating the metal mold with a chisel. This manner is useful as a first step. However, the method cannot used again and is not proper for processing hard materials and hardening materials. The beater method limits the part to be processed and depends on personal skill. Since the part hit by the chisel becomes thin, it is not durable.
A repair method by inserting die is reliable and has the advantage that the material can be changed when strength is required. However, it takes a long time to repair. When a flaw occurs on a cavity (or the product surface), a boundary of the inset die material appears on the product surface. In such a case, this method may not be used.
It is therefore an object of the present invention to provide a repair method with a welding wherein the welding is strong and the repaired part is durable and is not easily separated. The durability according to this invention is equal to or better than a metal member.
Another object of the present invention is to provide a repair method with a welding and a welding method that does not affect a portion of a metal member adjacent to a welded portion by heat. There is no blow hole, pit, under-cut, shrinkage, color change or the like in the portion repaired by the welding. Since the welded portion is noncorrosive, it is safe for workers.
It is a further object of the present invention to provide a repair method with a welding and a welding method that can weld in a relatively short time, does not melt and lose a metal member, needs less unnecessary welding metal, is easy to finish and allows a manual finishing.
It is an additional object of the present invention to provide a repair method with a welding and a welding method that is simple in process, is easy to start, and does not require a skilled worker. This invention does not require know-how, such as a remaining heat process, which requires a skilled worker. This invention can repair a cavity (or a surface of a formed product) through welding without the repaired mark.
It is another object of the present invention to provide a primary electrode for a welding that can attach the welding powder of a necessary volume to the portion to be repaired with the welding and makes the welding process easy. This invention improves an efficiency of the welding process. The primary electrode of the invention includes a magnet.